use a proper regex looking for the restartCount

pkg/kubelet/kuberuntime/kuberuntime_container.go

@@ -140,9 +140,9 @@ func calcRestartCountByLogDir(path string) (int, error) {
 		return 0, err
 	}
 	if len(files) == 0 {
-		return 0, err
+		return 0, nil
 	}
-	restartCountLogFileRegex := regexp.MustCompile(`(\d+).log(\..*)?`)
+	restartCountLogFileRegex := regexp.MustCompile(`^(\d+)\.log(\..*)?`)
 	for _, file := range files {
 		if file.IsDir() {
 			continue
@@ -153,7 +153,9 @@ func calcRestartCountByLogDir(path string) (int, error) {
 		}
 		count, err := strconv.Atoi(matches[1])
 		if err != nil {
-			return restartCount, err
+			// unlikely kubelet created this file,
+			// likely custom file with random numbers as a name
+			continue
 		}
 		count++
 		if count > restartCount {
@@ -200,7 +202,8 @@ func (m *kubeGenericRuntimeManager) startContainer(ctx context.Context, podSandb
 		logDir := BuildContainerLogsDirectory(pod.Namespace, pod.Name, pod.UID, container.Name)
 		restartCount, err = calcRestartCountByLogDir(logDir)
 		if err != nil {
-			klog.InfoS("Log directory exists but could not calculate restartCount", "logDir", logDir, "err", err)
+			klog.InfoS("Cannot calculate restartCount from the log directory", "logDir", logDir, "err", err)
+			restartCount = 0
 		}
 	}
 

pkg/kubelet/kuberuntime/kuberuntime_container_test.go

@@ -476,6 +476,48 @@ func TestRestartCountByLogDir(t *testing.T) {
 			filenames:    []string{"5.log.rotated", "6.log", "7.log"},
 			restartCount: 8,
 		},
+		// no restart count log files
+		{
+			filenames:    []string{},
+			restartCount: 0,
+		},
+		{
+			filenames:    []string{"a.log.rotated", "b.log.rotated", "12log.rotated"},
+			restartCount: 0,
+		},
+		// log extension twice
+		{
+			filenames:    []string{"145.log.log.rotated"},
+			restartCount: 146,
+		},
+		// too big of the integer
+		{
+			filenames:    []string{"92233720368547758089223372036854775808.log.rotated"},
+			restartCount: 0,
+		},
+		// mix of log files
+		{
+			filenames:    []string{"9223372036854775808.log.rotated", "23.log", "23a.log", "1aaa.log.rotated", "2.log", "3.log.rotated"},
+			restartCount: 24,
+		},
+		// prefixed
+		{
+			filenames:    []string{"rotated.23.log"},
+			restartCount: 0,
+		},
+		{
+			filenames:    []string{"mylog42.log"},
+			restartCount: 0,
+		},
+		{
+			filenames:    []string{"-42.log"},
+			restartCount: 0,
+		},
+		// same restart count multiple times
+		{
+			filenames:    []string{"6.log", "6.log.rotated", "6.log.rotated.rotated"},
+			restartCount: 7,
+		},
 	} {
 		tempDirPath, err := os.MkdirTemp("", "test-restart-count-")
 		assert.NoError(t, err, "create tempdir error")
@@ -484,8 +526,10 @@ func TestRestartCountByLogDir(t *testing.T) {
 			err = os.WriteFile(filepath.Join(tempDirPath, filename), []byte("a log line"), 0600)
 			assert.NoError(t, err, "could not write log file")
 		}
-		count, _ := calcRestartCountByLogDir(tempDirPath)
+		count, err := calcRestartCountByLogDir(tempDirPath)
-		assert.Equal(t, count, tc.restartCount, "count %v should equal restartCount %v", count, tc.restartCount)
+		if assert.NoError(t, err) {
+			assert.Equal(t, count, tc.restartCount, "count %v should equal restartCount %v", count, tc.restartCount)
+		}
 	}
 }